The present invention relates to civil engineering and road construction machinery, more particularly to a hydropneumatic hammer which operates by a reciprocal action of a percussive piston and a directional control valve.
In general a hydropneumatic percussive tool according to the prior art pertaining to this invention comprises a gas chamber so arranged in the upper position of the piston as to accumulate percussive energy by its compression during upstroke of the piston.
A delivered oil under pressure into a chamber which is generally made around the lower portion of a piston makes the piston move upward compressing the gas contained in the gas chamber until it reaches its full upstroke position and when the piston reaches its full upstroke position, another chamber which is generally provided around the upper portion of the piston is filled with a pressurized oil by an operation of a directional control valve and this causes the pressure of oil acting on said lower-positioned chamber to be countervailed and results in revelation of the accumulated energy of the gas and accordingly the piston comes to drop instantaneously to strike the head of the percussive rod disposed coaxially with the piston.
The kind of device as described above generally needs special components such as a valve plug or a valve cock to convert the valve and it further needs very complicated passageways like a maze to make the upper-positioned chamber become filled with a fluid under pressure to drop the piston.
Consequently the device of this type is commonly disadvantageous in that it is large in size and heavy in weight because of use of the special components to operate the control valve and the complicated passageways for the fluid to travel and these disadvantages also result in the high cost of production as well as the frequent and difficult repair work.
In the field of hydraulic engineering, it should be noted that long and/or crooked passageways for fluid deteriorate the energy efficiency of the device while on the other hand, short and direct ones were found to be highly advantageous.
It is therefore an object of the present invention to make the percussive tool which is operated in a hydropneumatic manner to be small in size, light in weight and simple in construction, and also to be minimal in cost of production.
Another object of the present invention is to improve the efficiency of the device by adoption of simplicity of passageways.
Still another object is to improve the operational stability and the reliability of the device.